Responsiveness of human prostate carcinoma bone tumors to interleukin-2 therapy in a mouse xenograft tumor model

We have tested an immunotherapy approach for the treatment of metastatic pr ostate carcinoma using a bone tumor model. Human PC-3 prostate carcinoma tu mor cells were heterotransplanted into the femur cavity of athymic Balb/c n ude mice. Tumor cells replaced marrow cells in the bone cavity, invaded adj acent bone and muscle tissues, and formed a palpable tumor at the hip joint . PC-3/IF cell lines, generated from bone tumors by serial in vivo passages , grew with faster kinetics in the femur and metastasized to inguinal lymph nodes. Established tumors were treated with systemic interleukin-2 (IL-2) injections. IL-2 significantly inhibited the formation of palpable tumors a nd prolonged mouse survival at nontoxic low doses. Histologically IL-2 caus ed vascular damage and infiltration of polymorphonuclear cells and lymphocy tes in the tumor as well as necrotic areas with apoptotic cells. These find ings suggest destruction of tumor cells by systemic IL-2 therapy and IL-2 r esponsiveness of prostate carcinoma bone tumors.